1. A yellow light of wavelength 590nm is directed at a plane transmission grating. If the angle of the third order bright fringe is 32度, estimate the number of lines in 1 cm of the grating.
2. When monochromatic light(wavelength is 660 nm) passes through a double-slit(slit separation is 0.15 mm), an interference pattern is formed on the screen which is 1 m in front of the double-slit.
(a). What is the distance between the 2nd and the 5th bright fringe?
(b). What is the distance bwtween the central bright fringe and the 3rd dark fringe?
3. A student directs orange light at a plane transmission grating(3200 lines per cm). The pattern is projected on a screen which is 1 m from the grating.
(a). If the distance of the third order bright fringe from the zeroth order bright fringe is 0.7 m, what is the angle of the third order bright fringe?
(b). Find the wavelenght of the orange light.
物理 wave
2011-09-13 3:32 am
回答 (1)
2011-09-13 9:32 am
✔ 最佳答案
1. a.sin(32) = 3 x 590where a is the grating line separation
i.e. a = 3340 nm = 3.34 x 10^-4 cm
hence, no. of lines per cm = 1/3.34x10^-4 = 2993
2. (a) Distance between 2nd and 5th bright fringes
= (5-2) x 660 x 1000/0.15 nm = 1.32 x 10^7 nm = 1.32 cm
(b) Distance of 3rd dark fringe from central bright fringe
= (3-1/2) x 660 x 1000/0.15 nm = 1.1x10^7 nm = 1.1 cm
3.(a) angle of 3rd order bright fringe = arc-tan(0.7/1) = 35 degrees
(b) grating line separation, a = 1/3200 cm = 3.125x10^-4 cm
hence, (3.125x10^-4) x sin(35) = 3入, where 入 is te wavelength of orange light
hence, 入 = 5.975x10^-5 cm = 597 nm
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